DAKAR, Nov 20 (Reuters) - The world's longest-ruling leader, President Teodoro Obiang of Equatorial Guinea, staged a vote on Sunday to extend his 43-year-rule of a tiny, authoritarian African state where once plentiful oil wealth has been in a rapid decline."What you sow is what you reap," said Obiang, 80, who has regularly won more than 90 percent of the vote in elections conducted over the course of five terms since he seized power from his uncle in a coup in 1979.Two opposition candidates are standing: Buenaventura Monsuy Asumu, who has already stood in the previous five elections, and Andrés Esono Ondo, an opposition figure running for the first time.He said some semblance of fair voting was taking place in the island capital Malabo, but his party had evidence that officials elsewhere were casting ballots on voters' behalf or forcing them to vote for the ruling party.Maja Bovcon, a senior Africa analyst at risk intelligence company Verisk Maplecroft, said the election outcome was in no doubt: "The closure of the borders and the harassment and arrests of opposition supporters have been paving the way for the extension of Obiang's 43-year rule.""